Data mile
In radar-related subjects and in JTIDS, a data mile is a unit of distance equal to 6000 feet. An international mile is exactly 0.88 of a data mile.
The speed of light is 983571056 ft/s, or about one foot per nanosecond. If it were exactly one foot per nanosecond, and a target was one data mile away, then the radar return from that target would arrive 12 microseconds after the transmission.
